Drivers who have no alcohol in their system the morning after a night of drinking can be equally as impaired as those drivers who still have a residual alcohol trace.

Research commissioned by insurer RSA found that drivers were more prone to speed, spend longer speeding and committed more traffic violations while driving in the morning after a heavy night out.

The study, conducted at Brunel University, used 11 students who each drank an average of 7.1 units of alcohol the night before the test.

The following morning, at 9am, they underwent a trial on Brunel’s driving simulator to test their reactions and performance.

During the 4.7-mile simulator driving test, the hungover students drove faster (an average of 41.7mph compared to 32.6mph when sober), spent longer driving over the speed limit (1.2 miles compared to 0.3) and were more likely to veer out of lanes.

Psychologist Dr Mark Young, of the Human-Centred Design Institute at Brunel, said: “It does not matter if a driver has zero or some alcohol in their system.

“They could have a breath test and pass but still be impaired.”

Dr Young said that a significant factor in hungover driving is tiredness, with alcohol affecting the quality and duration of sleep.

This then affects attention and concentration levels, as well as visual-spatial performance – a key skill in driving.

The scale of hungover driving is huge, with 80% of drivers questioned in an AA poll admitting they may have been over the drink-drive limit the morning after (Fleet News, December 29).